1. Field of the Invention
The present invention relates to the preparation of crimped tow using a stuffer box in combination with a pair of crimping rollers to feed molded tow to the stuffer box. The stuffer box includes an initial first region adjacent to the rollers for crimping, and a second region for application of finish. The application of finish subsequent to the crimping process improves the crimping of the fiber as well as adherence of the finish to the fiber.
2. Prior Art
In prior art apparatuses, continuous filament tow is typically pulled, dewatered, rectangularly molded and fed by a single pair of smooth cylindrical parallel rotatable crimping rollers in conjunction with side plates, into a rectangular stuffer box referred to in some references as a crimping chamber. The stuffer box generally forms a substantially rectangular closed pressure zone having a weighted discharge flapper at the exit thereof. As the tow is fed by the crimping rollers into the stuffer box, the filaments bend back and forth upon itself and against the resistance of the inner walls of the stuffer box, forming a crimped wad. This wad is compressed in its passage through the stuffer box by the friction of the sidewalls and the weighted discharge flapper. The action of the crimping rollers in continuously feeding tow into the chamber produces crimps in the tow, which can be later effectively set by heat or fluid treatment. Or in the alternative, the crimp can be set by the introduction of steam into the chamber. The crimped tow is discharged from the stuffer box at a rate proportionate to the infeed of the crimping rollers.
Optimally, crimped tow material is produced when resistance to the rectangularly molded tow by walls of the stuffer box is evenly distributed. One factor in achieving even resistance is by having uniform finish on the fiber. Some applications of finish require a slick finish to be applied, which diminishes the resistance of the fiber within the stuffer box.
The following references are directed to various apparatuses used for crimping filament or fiber tow, that include at least a stuffer box and crimping rollers. U.S. Pat. No. 3,911,539 to Hughes et al, discloses a method and apparatus for crimping tow incorporating the injection of steam in various regions within the stuffer box to set the crimp in the tow. In particular, the stuffer box has three various regions into which various pressures of steam are injected to acquire superior crimp products. Also, it is noted within the disclosure, that finish may be applied to the fibers through spinning and/or drawing steps, and/or also prior to the crimping.
Other references directed to improving the crimping through the injection of steam, include U.S. Pat. Nos. 3,643,298; 3,305,897, and 4,122,019. Also known as prior art is the inclusion of holes in the stuffer box downstream of the steam injection ports wherein the holes allow for escape of the steam to control pressure buildup in the stuffer box. Also, it is known that finish can be injected through the steam injection ports.
Application of a slick finish prior to the crimping apparatus has been found to increase the difficulty in crimping the tow due to the slickness of the tow. Also, the application of finish to the tow through the steam injection ports has been found to be unsatisfactory based on the distribution of the finish on the tow and crimping of the tow. The problem addressed by the present invention is uniform crimping of slick finished tow.
The foregoing prior art fails to address the issue of the application of finish to the tow subsequent to the crimping of the tow. There remains a need to develop an apparatus for the stuffer box crimping that will not only improve the crimping of the tow, but permit application of finish subsequent to the crimping process.
It is a further aim or aspect of the present invention to improve the quality of this stuffer box crimped tow material by application of the finish subsequent to the crimping.